What are the Ottawa ankle rules (Ottawa criteria) for determining the need for radiography in patients with ankle pain?

Ottawa Ankle Rules for Determining Need for Radiography in Ankle Pain

The Ottawa Ankle Rules recommend that ankle radiographs are only required when there is pain in the malleolar region AND either bone tenderness along the distal 6 cm of the posterior edge or tip of either malleolus, OR inability to bear weight for four steps both immediately after injury and in the emergency department. 1

Ankle Rules Criteria

• An ankle radiograph series is required only when there is bone tenderness along the distal 6 cm of the posterior edge of either malleolus 1
• An ankle radiograph series is also required when there is inability to bear weight immediately after injury and in the emergency department 1
• The Ottawa Ankle Rules have a sensitivity of 96.8-100% for detecting clinically significant fractures 1
• Adding swelling as a criterion increases sensitivity to 100% for the malleolar zone 1

Foot Rules Criteria

• A foot radiograph series is required only if there is pain in the midfoot AND any one of the following: 1, 2
  • Point bone tenderness of the navicular 1, 2
  • Point bone tenderness of the base of the fifth metatarsal 1, 2
  • Inability to bear weight or walk 4 steps immediately after injury or in the emergency department 1, 2

Clinical Performance

• The Ottawa Ankle Rules have demonstrated a sensitivity of 96.8-100% for detecting clinically significant fractures 1, 3
• Specificity ranges from 16-51%, with studies showing potential reduction in unnecessary radiographs by approximately 30-35% 1, 3, 4
• A 2021 study confirmed that implementation of these rules prevents patients from unnecessary radiation exposure 4

Exclusionary Criteria

• The Ottawa Rules should not be used or should be used with great caution in patients with: 1
  • Penetrating trauma 1
  • Pregnancy 1
  • Skin wounds 1
  • Patients transferred with radiographs already taken 1
  • Injuries >10 days old 1
  • Return visits for continued traumatic foot pain 1
  • Polytrauma 1
  • Altered sensorium 1
  • Neurologic abnormality affecting the foot 1
  • Underlying bone disease 1

Age-Specific Considerations

• The rules are validated for patients >5 years of age 1
• For geriatric patients (≥65 years), some research suggests modifying the rules to mandate imaging for all elderly patients with ankle pain, as this increases sensitivity to 99% 5
• The specificity in geriatric patients is lower (33.33%) compared to non-geriatric patients (60.13%), suggesting a higher rate of false positives in older adults 5

Radiographic Views When Indicated

• When X-rays are indicated based on the Ottawa Ankle Rules, three standard views should be obtained: anteroposterior, lateral, and mortise views 1
• The views should include the base of the fifth metatarsal bone 1
• Weight-bearing radiographs, if possible, provide important information for fractures of uncertain stability 1

Potential Modifications

• The "Buffalo" modification has been proposed to improve specificity for malleolar fractures (59% vs 42% with standard Ottawa rules) while maintaining 100% sensitivity 6
• Some studies suggest that when weight bearing is the sole positive criterion, reassessment after several days may be reasonable to avoid unnecessary radiation exposure 4

Occult Fractures

• In patients with positive Ottawa Ankle Rules but negative radiographic findings, 3D-CT may detect occult fractures not visible on standard radiographs 3
• One study found that of 21 patients with positive OAR results and negative radiographic findings who underwent 3D-CT, five had occult fractures of the lateral malleolus 3